justice kagan why this dispute is not classic case to deference tohe agency. the agency gs to choose how to make tng work as best it can? when the change makes it not work entirely as congress foretold. >> the epa chose to try timely meant the broad protective goals of the statute by bending a little bit on the implementation side. i think tt's a choice that agencies have to be able to make. >> scores ever businesses, states, led by texas and several gop lawmars are characterizing what happened as an unprecedented power grab and calling on the justices to restore what they argue is the rightful balan between the branches. >> from a constitutional perspective this is a wholly troubling practice that needs to be rectified by the high court. >> as is so often the case here at the court the swing vote could be justice anthony kennedy the last time there was a major challenge to epa regulatory here at the court he sided with the agency. but today at the federal government came to the close of its arguments, he said i read all your briefin and i see no case anywhere